Yet emerging from an uninspiring election campaign that avoided tough issues, where "consensus" was the watchword of all five parties save Die Linke, and where 25 percent of voters are undecided – the party headed by fiery Oskar Lafontaine could bring a surprise. They are already bringing a recalculation of post-election politics.

Die Linke's election motto is "Wealth for all." Known in English as the Left party, its support has shot up from 4 percent to 14 percent in polls since the 2006 elections, and is surging after a good showing in local elections three weeks ago. They attract workers, are popular in eastern Germany, and worryingly for the establishment represent a "protest vote" among Germans desiring a clearer voice for "social justice."

Die Linke is the only party calling for German withdrawal from Afghanistan – an issue that could be a sleeper, though it hasn't shown up in polls yet.

The Left sees its fellow left Green party as bourgeois-bohemians – well-intentioned eco-softies that came to Berlin to do good, and stayed to do well.

"Many people falling through the social system feel that something is not right in our society," says Klaus Lederer, the fervent young head of Die Linke in Berlin, in an interview. "We've heard for years there's no money for social needs. But apparently now there's a lot of money for the banks!"

"We are a transforming party," says the lanky Mr. Lederer, who has two thin earrings in his left lobe and was 15 years old when the Wall fell. He sees Die Linke as a more honest standard-bearer of leftist values than the mainstream Social Democratic Party (SPD), a partner with Chancellor Angela Merkel's conservative Christian Democrats in her coalition government.

"With the SPD not standing for social justice any more, we are forcing them to remember a past that included peace and social equality."

However, the Left also represents a past many Germans would like to forget. In recent months Gregor Gysi, the party leader, has been charged with being an informer for the Stasi, or secret police, in the former East Germany. The Left views these charges, 20 years since reunification and during a political campaign, as demagoguery from the right.

But it is an issue that resonates. As Lederer says about the communist past of his party: "Yes, that is a problem. We've moved from a Stalinist party to a democratic socialist party. We've had to be responsible for a history that is still a living memory. But that's a significant evolution – and we bring that experience of rethinking and evolving to the table."

But opponents and some Germans worry that Die Linke's ideology is not entirely divorced from its darker East German history.

"I'm not sure that party [Die Linke] thinks that East Germany was really so bad," says Karl Georg Wellmann, a CDU representative from west Berlin. "They don't say the Stasi was so bad. They think the Wall had some good sides to it. [Leader Gregor] Gysi worked for the Stasi ... in a high level position. I don't trust them, and a lot of Germans don't trust them."

Is the left ready?

The political class in Berlin, in general, does not consider Die Linke ready for prime time. "They know nothing about governing or about how to run a modern economy," says one senior official of the CDU.

Lederer admits the party is still a work in progress, with many fights among many factions – older Marxists and what he calls "conspiracy theorists." But a new Die Linke is in the process of forming, he says. This week Dietmar Bartsch, a Left Party senior official, showed some late-campaign flexibility on foreign policy issues, telling the daily Tagesspiegel that "When we say 'out of Afghanistan' we don't mean 'get out of Afghanistan the day after tomorrow.'"

A strong showing by Die Linke on Sunday could hasten a political realignment in Germany, analysts say. If Merkel's CDU does not form a coalition with the liberal Free Democrats Party (FDP), a safe "center-right" coalition – there is a likely return to the current "grand coalition" of SDP and CDU. But political dynamics on the left are considered likely to pressure the SPD to consider leaving the coalition and to join with the Greens and Die Linke.